Investigating the Structure of Ce1?x La x CoIn5 Using NQR

We report NQR data on the heavy-fermion compound Ce _x La_1?x CoIn₅. The NQR spectrum of the In(1) site is composed of five different peaks, which are described by a binomial distribution of the nearest-neighbor La atoms. Our results suggest that an analysis of the NQR spectra yields a more accurate doping level than energy dispersive X-ray spectroscopy (EDS) results.     

Preparation and Structure of Ga2 – x Sc x O3 (0.42 ≤ x ≤ 0.52)

The structure of a scandium gallium oxide single crystal grown by the Czochralski process from a charge of composition Ga_1.5Sc_0.5O₃ is determined by x-ray diffraction. The structure is shown to be a superstructure to -Ga₂O₃. The superstructure parameters are found to vary both along the axis of the crystal and radially, which is due to variations in Ga : Sc ratio. A structural model of the Ga_1.5Sc_0.5O₃ crystal is proposed.     

Structure and stability of rapidly quenched Al86Cr14−x Fe x alloys

The structural and thermal properties of melt spun Al₈₆Cr_14–x Fe _x , alloys have been investigated using X-ray diffraction, transmission electron microscopy, electron diffraction and differential thermal analysis. Electron diffraction patterns indicate that all alloys contain quasicrystalline nodules with icosahedral symmetry in a matrix of f cc aluminium. Microscopically the alloys fall into two categories; those with x 6 and those withx > 6. The first class alloys shows large (>1m) icosahedral crystallites with well defined dendritic crystallite growth and sharp quasicrystalline X-ray diffraction peaks. The latter alloys show quasicrystalline crystallites which are predominantly much smaller as well as considerably broadened X-ray diffraction peaks. Thermal analysis measurements indicate that the activation energy for crystallization in these alloys is about 1.5 eV.     

Structure and Properties of Nonstoichiometric La1 – x Na x MnO3 ± γ Solid Solutions

The structural, electrical, magnetic, and magnetoresistive properties of polycrystalline La_{1 – x} Na _x MnO_{3 ±} are studied in the range 0.08 x 0.16. The solid solutions contain La and O vacancies and crystallize in the space group R3¯c. The Curie temperature of the solid solutions depends not only on the formal charge state of Mn but also on the Na content, the amounts of La and O vacancies, and synthesis conditions. The synthesized materials are potentially attractive as room-temperature magnetic sensors.     

Structure and dielectric properties of Nd x Sr1−x TiO3 ceramics for energy storage application

Polycrystalline Nd-doped SrTiO₃ ceramics with the formula Nd _x Sr_1?x TiO₃ (NSTO, x = 0, 0.024, 0.056, 0.104, 0.152, 0.200) were prepared by solid state reaction route. X-ray diffraction (XRD) analysis confirmed the formation of monophasic compounds and indicated the structure to be changed from cubic to tetragonal by increasing Nd doping concentrations. A remarkable decrease in grain size from ~30 μm for un-doped SrTiO₃ ceramics to ~1 μm for Nd-doped SrTiO₃ ceramics with x = 0.024 was observed by scanning electron microscopy. The grain size had a degree of increasing with further increasing Nd doping concentration and reached ~3 μm when the x value was 0.200. The dielectric properties of NSTO ceramics were measured at 1 kHz in ambient temperature. It revealed that the dielectric constant dramatically increases for the reason of Nd doping, leading to a maximum value of 19,800 for as-sintered sample with x = 0.104. The breakdown strength of all Nd-doped SrTiO₃ samples was found to be higher than 10 kV/mm. The relationship between dielectric properties and the microstructure feature, as well as the defect structures correlated with the charge compensation induced by trivalent Nd³⁺ doping, was discussed tentatively.     

Structure and properties of Titanium–25 Niobium–x iron alloys

The present work studies the effect of iron on microstructure, mechanical properties and corrosion behavior of Ti–25Nb based system with emphasis on improving strength/modulus ratio. Experimental data shows that cast Ti–25Nb–3Fe has a phase with a entirely of dendrite morphology. The bending strength/modulus ratio is 24.6 higher than Ti–6Al–4V (17.4) by 41.4% and than c.p. Ti (9.3) by 165%. The critical anodic current density of the metal in 37 °C Hanks solutions is lower than approximately 100 A/cm². Ti–25Nb–3Fe alloy has a great potential for use as an implant material.     

Study of Band Structure Properties of Pnictide LaO1−xF x FeAs (x = 0, 0.2) Superconducting Compound

This paper reports on the band structure properties and changes in band structure of fluorine-doped LaO_1?x F _x FeAs (x = 0, 0.2) compound, measured using X-ray photoemission spectroscopy (XPS). The band structure of the superconducting compound is compared with nonsuperconducting parent compound LaOFeAs. With fluorine doping, a shift of the shallow core level is observed in XPS spectra, which may be a response of the band structure due to fluorine doping in the system. The balance of the chemical potential shift with the screening effect of conduction electrons near the Fe and As ions is discussed using nearly unchanged Fe 2p and As 3d core-level spectra. The La 3d core-level spectra shift towards the high energy, ～0.36 eV, may be due to the chemical potential shift caused by fluorine doping. In our valence band spectra, a small peak at around 0.2 eV is observed, which disappeared with the fluorine doping in the system, indicating a change of Fe 3d state from low spin to high spin states and also confirming the nature of Fe 3d electrons as itinerant, which is responsible for superconductivity in these compounds.     

Structure and Charge-Transfer Mechanism in Y1?x Ca x Ba2Cu3O7?δ Through Direct Doping

Here we study the effect of Ca doping on the charge-transfer mechanism of polycrystalline YBa₂Cu₃O_7??? compound. The samples of composition Y_1?x Ca _x Ba₂Cu₃O_7??? (x=0.00,0.05,0.10,0.20 and 0.30) are synthesized through standard solid-state reaction route. Carrier doping is controlled by annealing of samples in oxygen and subsequently in reducing atmosphere. Samples are investigated using resistivity, dc magnetization (M?CT) and magnetization with field (M?CH) measurements. With increase of Ca the transition temperature (T _c) decreases in oxygenated samples, whereas the same increases in reduced samples. Further reduction of samples at higher temperatures (>600?°C) though results in non-superconducting nature up to Ca concentration of x=0.20, the x=0.30 sample is superconducting below 30?K. This provides a remarkably simple and effective way to study the relationship between structure, superconductivity, and associated electronic properties. Variation in Cu₁?CO₄, Cu₂?CO₄ and Cu₂?CO₂ bond lengths with oxygen content, is seen through the structural refinement of XRD pattern. The effective coordination of Cu₂ atom with oxygen changes with the change in these bond lengths and hence the holes in the CuO₂ planes. The charge-transfer mechanism from CuO _x chains to CuO₂ planes and thus effective hole doping is discussed in the context of the results observed.     

Effects of Chemical Composition and Sintering Temperature on the Structure of La1 – x Sr x MnO3 ± γ Solid Solutions

The structural parameters of La_{1 – x} Sr _x MnO_{3 ±} solid solutions sintered at different temperatures are refined using chemical analysis, x-ray fluorescence, and Rietveld profile analysis data. The samples are shown to consist of two rhombohedrally distorted perovskite phases (sp. gr. R c and R3m) identical in chemical composition and containing excess oxygen. The electrical properties and magnetoresistive response of the Sr-doped lanthanum manganite ceramics depend on the relative amounts of these phases. The origin of structural disordering in the materials studied is discussed.     

The Effects of Doping on Crystal Structure, Magnetic and Microwave Properties of SrFe12−2x La x (Mn0.5Zr0.5) x O19 Nanoparticles

M-type hexagonal ferrite powders, SrFe_12?2x La _x (Mn_0.5Zr_0.5) _x O₁₉ (x=0.0, 0.2, 0.4, 0.6, 0.8), have been synthesized by the coprecipitation method. The X-ray diffraction, field emission scanning electron microscope, vibrating sample magnetometer and vector network analyzer all were used to characterize the structure of the samples, their magnetic and microwave properties. The value of the saturation magnetization increased up to x=0.2 and then slowly decreased with increasing doping. A decreasing trend was observed in the value of coercivity with increasing substitution degree, and its value reached a minimum of 2420 Oe for x=0.6 and then increased with further increasing x. The relative complex permittivity and permeability of the composite powders were investigated in the X-band frequency range (8.2–12.4 GHz).     

Local Atomic and Electronic Structure with Magnetism of La0.7Ca0.3Mn1?x Cu x O3 (x=0, 0.03, 0.06, 0.1)

Local atomic and electronic structure with magnetic properties, especially Griffiths phase, of polycrystalline samples La_0.7Ca_0.3Mn_1?x Cu _x O₃ (x=0, 0.03, 0.06, 0.1) have been studied. The X-ray absorption spectra (XAS) of Cu 2p core level prove that the valence state of Cu ions exhibits trivalent state when doping content x≤0.06 and divalent Cu²⁺ ions begin to show for x=0.1. For the valence states of Mn ions, the X-ray photoelectron spectroscopy data show that they are in mixed states of Mn³⁺ and?Mn⁴⁺, and a shift to lower binding energy is observed, which is not attributed to the variation of valence states of Mn ions but the change of crystallographic surroundings, because there is no obvious change detected by X-ray absorption fine structure spectroscopy (XAFS). The Debye-Waller factor (σ ²) of x=0.1 sample is only slightly larger compared to x=0, which may be the origin of enhancement of Griffiths phase observed in the inverse-susceptibility as a function of temperature (H/M～T). The H/M～T curves of Cu doped samples indicate coexistence of FM, AFM and PM phase above Curie temperature?T _C , which may be related to the strong hybridization of O 2p and Mn 3d reflected by O 1s XAS spectra.     

Structure of Mo2.0 – x Ni1.0 + x P (x = 0.2) and Some Crystal-Chemical Features of Ternary Phases in the Mo–Ni–P System

The crystal structure of Mo_{2.0 – x} Ni_{1.0 + x} P (x= 0.2) is determined by powder x-ray diffraction (monoclinic symmetry, new structure type, sp. gr. Im, a = 1.04036(5) nm, b= 0.84055(4) nm, c= 0.47357(2) nm, = 91.538(3)°; R _int = 0.094, R _prof = 0.197). The 850°C section of the Mo–Ni–P phase diagram is studied in detail, and the crystal-chemical features of molybdenum nickel phosphides are discussed.     

Structure,properties and morphological studies of indium intercalation compounds of tungsten disulphide,In x WS2 (0 ⩽¡x ⩽ 1)

A detailed investigation of crystal structure, properties and morphological characteristics of indium intercalation compound of tungsten disulphide, In_xWS₂ (0 × 1) is reported. X-ray analysis shows that intercalated compounds, like the host 2H-WS₂, also possess hexagonal symmetry with a small but continuous increase inc-lattice parameter. Room-temperature thermoelectric power experiments and low-temperature (150 to 300 K) conductivity measurements indicate that intercalated compounds also exhibit p-type semiconducting behaviour similar to base material WS₂. Thermal stability behaviour of these compounds in air and argon atmosphere has been studied and based on the X-ray data of oxidized products, formation of tungsten bronzes has been proposed. Results of the SEM study are also reported.     

Structure and piezoelectric properties of lead-free (Na0.52K0.44−x )(Nb0.95−x Sb0.05)O3-xLiTaO3 ceramics

Lead-free (Na_0.52K_0.48?x )(Nb_0.95?x Sb_0.05)O₃-xLiTaO₃ (x = 0.025–0.05) piezoelectric ceramics in which the Sb content is kept constant, have been specially designed and successfully fabricated by a conventional solid state reaction method. The (Na_0.52K_0.48)(Nb_0.95Sb_0.05)O₃ ceramics can be well sintered after A-site and B-site cations are replaced by Li⁺ and Ta⁵⁺, respectively. A single-phase perovskite structure remains within the studied substitution concentration. An orthorhombic-tetragonal phase transition occurs with gradually increasing the content of Li⁺ and Ta⁵⁺, and was identified in the composition range of 0.0375 < x < 0.0425 where two kinds of ferroelectric phases may coexist and simultaneously a strong compositional dependence of electrical properties was found out. An appropriate content of Sb effectively enhanced the piezoelectric properties of the materials. The optimum overall properties with a piezoelectric constant d ₃₃ of 321 pC/N, a dielectric constant $ \varepsilon_{33}^{T} $ of 1,780, a planar electromechanical coupling coefficient k _p of 0.52 and a Curie temperature T _c of 315 °C were obtained in the composition with x = 0.0425, indicating the ceramics studied have potentials for replacing lead-containing ceramics for device applications.     

Pb1−x Bi x /Bi/Pb1−x Bi x Josephson junction

A superconductor/semimetal/superconductor (S/SM/S) Josephson junction has been developed. We have used an alloy of Pb_1–x Bi _x (0x 0.6) as the superconductor and Bi as the semimetal. By irradiating at X-band microwave of 10 GHz, Shapiro steps were observed for various bismuth barrier thicknesses inÅ and bismuth weight ratiosx. Finally, we obtained the empirical relationship for barrier thickness, below which microwaves could be detected for various bismuth weight ratiosx at the temperature of 4.2 K.     

Lattice-matched epitaxial Pb1 − x Mn x Se/PbSe1 − x S x heterojunctions

This paper examines the possibility of producing lattice-matched p-n heterojunctions based on epitaxial n-Pb_{1 ? x} Mn _x Se (x = 0.02) and p-PbSe_{1 ? x} S _x (x = 0.04) films. The heterojunctions have been grown by molecular beam epitaxy in a single processing cycle, without breaking the vacuum, using a compensating Se vapor source in the growth process. Optimal conditions have been found for the growth of structurally perfect (W _1/2 = 90″-100″) epitaxial films and fabrication of lattice-matched heterojunctions based on such films, photosensitive in the IR spectral region.     

Thermodynamic properties of Ca1 − x Er x F2 + x and Ca1 − x Yb x F2 + x heterovalent solid solutions

The heat capacity of single crystals of the Ca_{1 ? x} Er _x F_{2 + x} (x = 0.05, 0.10) and Ca_0.95Yb_0.05F_2.05 fluorite solid solutions was determined by adiabatic calorimetry in the temperature range 55–300 K. The results were used to obtain temperature dependences of the Debye characteristic temperature, entropy, and enthalpy for the solid solutions.